1. Field of the Invention
This invention relates to synchronizing signal detecting apparatus for circular knitting machines or more in particular to a mechanical synchronizing signal detecting apparatus for circular knitting machines having an electronic pattern-forming command circuit.
2. Description of the Prior Art
In conventional circular knitting machines having an electronic pattern-forming command circuit, a control signal processed electronically in accordance with a desired pattern is applied to a needle selecting system in synchronism with the movement of the needle track of the machine. In order to detect the movement of this needle track of the machine, a needle track detector produces a sine-wave signal in synchronism with the pitches of the needle track. At the time point when this sine-wave signal passes the zero level from negative to positive side, a control signal indicating "Knit" or "Don't knit" is applied to the needle selecting system of the machine.
A minute backward motion of the machine has so far been unavoidable immediately following the stoppage thereof from a normal operating condition. In the event that the position of such a stoppage happens to be immediately after the passing of the zero level by the detected sine-wave signal, the sine-wave signal passes the same zero level again at the time of reactuation or restarting of the machine, thus erroneously producing one superfluous pulse of the synchronizing signal, with the result that a control signal displaced by one step is applied to the needle selecting system. This erroneous operation has been one of the causes for the reduction in quality due to dispersion of pattern.